1. Field of the Invention
The present invention relates to processors (microprocessors or microcontrollers) and more particularly to a debugging interface integrated into a processor.
2. Description of the Related Art
Such a debugging interface enables an external emulator to be connected to the processing unit of the processor and instructions to be executed to be sent to it. The processor comprises a debugging mode in which the debugging interface is active and provides the processing unit with instructions received from the external emulator. The instructions supplied to the processor by the debugging interface then replace the instructions coming from the program memory.
For this purpose, the debugging interface generally comprises a set of internal data transfer, control and status registers, which are accessible to the external emulator through an external port. The external port conforms, for example, to the standard IEEE 1149.1 also referred to as JTAG (Joint Test Access Group). The control register stores commands received from the external emulator to be applied to the debugging interface. The status register supplies the external emulator with information about the status of the debugging interface. The data transfer registers save data and commands to be executed by the processing unit, coming from the external emulator, and data coming from the processing unit towards the external emulator.